Microbial Community Characteristice Of Different Forest Types And Their Relationship With Environmental Factors In Permafrost Regions Of Daxin'anling

Microorganisms play an extremely important role in the biogeochemical cycle of permafrost and can be used as early warning and sensitive biological indicators for ecosystem changes in cold regions.Under the background of global warming,the degradation of permafrost was bound to directly or indirectly affect soil microorganisms and soil processes regulated by microorganisms,thus changing the structure and function of forest ecosystems in permafrost regions.Taking soil microorganisms in permafrost region of Daxing' anling as the research object,systematically analyzed different forest types(Larix gmelinii forest,Pinus sylvestris forest and Betula platyphylla forest)soil microbial community structure and diversity characteristics,To explore the internal relationship between frozen soil microorganisms and environmental factors,In order to objectively understand the response law of forest ecosystem to permafrost degradation in cold regions.To provide a scientific basis for predicting and analyzing the impact of future climate.1.The results of PLFA showed that 32 species(Larix gmelinii forest),33 species(Pinus sylvestris var.mongolica forest)and 36 species(Betula platyphylla forest)of PLFA were detected respectively.Bacteria were the dominant group(83.78%-90.55%),fungi were the second(5.87%-12.48%)and actinomycetes were the least(2.47%-3.90%).Total phospholipid fatty acids,Gram-positive bacteria,Gram-negative bacteria,fungi and actinomycetes were the highest in Betula platyphylla forest and the lowest in Pinus sylvestris var.mongolica forest.Shannon diversity index was highest in Betula platyphylla forest(3.09),lowest in Pinus sylvestris var.mongolica forest(2.927),the highest in Larix gmelinii forest(6.297)and the lowest in Pinus sylvestris var.mongolica forest(4.238).Principal component analysis(PCA)showed that the first and the second principal components that explained 77.9% of the total variation of soil microbial community structure.There were significant differences in soil microbial community structure among different types of forests.2.The results of Illumina high-throughput sequencing showed that 79714 effective bacterial sequences were detected in the three types of forests,belonging to 43 phyla,147 classes,285 orders,458 families and 671 genera.The relative abundances of Dominant soil bacterial flora among different forest types were different at phylum level.Proteus had the highest relative abundances in Betula platyphylla forest(38.86%)and the lowest in Pinus sylvestris var.mongolica forest(33.18%).Acidobacteria had the highest relative abundances in Betula platyphylla forest(38.44%)and the lowest in Larix gmelinii forest(16.25%).Chao abundance index and Shannon diversity index were the highest in Pinus sylvestris var.mongolica forest,which were 16082 and 10.142.respectively,and the lowest in Betula platyphylla forest,which were 9703 and 8.660,respectively.A total of 59 357 fungal sequences were detected into three different forest types,which belonged to 10 phyla,32 classes,93 orders,201 families and 393 genera.The relative abundance of dominant soil fungi flora varied among different forest types,with basidiomycetes being the highest(60.63%)in Betula platyphylla forest and the lowest(42.27%)in Larix gmelinii forest,ascomycetes being the highest(51.20%)and Betula platyphylla being the lowest(37.76%)in Larix gmelinii forest,and Chao flora being the lowest(37.76%)in Larix gmelinii forest.Leaf pine forest was the highest(1929),Pinus sylvestris var.mongolica forest was the lowest(1580),Shannon diversity index was the highest(7.035)in larch forest and the lowest(5.405)in birch forest.3.Redundancy analysis on different types of forests in permafrost region in Daxingan Mountains between soil microbial community structures and factors of soil environmental showed that total phospholipid fatty acids,Gram-positive bacteria,Gram-negative bacteria and bacteria were significantly positively correlated with the quantity of water,total nitrogen and total organic carbon(P<0.05),and negatively correlated with C/N ratio and pH value.Bacteria and actinomycetes were positively correlated with ammonium nitrogen,nitrate nitrogen and total phosphorus(P<0.05).Redundancy analysis of soil bacterial flora and environmental factors showed that Proteobacteria was positively correlated with total phosphorus(P<0.05),Acidobacteria was positively correlated with soil water content and total nitogen(P<0.05),Actinbacteria was positively correlated with pH(P<0.05),Redundancy analysis of soil fungi flora and environmental factors showed that Basidiomycetes was positively correlated with the total phosporus(P<0.05),Ascomycetes was positively correlated with the soil water content and total nitrogen(P<0.05),Zygomycota was positively correlated with ammonium nitrogen(P<0.05).